An ace is a playing card. In the standard deck, an ace has one suit symbol (a heart, a diamond, a spade, a club) in the center of the card, sometimes large and decorated, especially in the case of the ace of spades. In most card games, aces have the highest value of all cards in a suit; in some, the lowest.

An ace is also a military aviator who has shot down five or more enemy aircraft. The term originated in World War I in French newspapers. The leading German ace in that war was Rittmeister (Captain) Manfred von Richthofen, the "Red Baron", of the German air force, who was credited with downing 80 Allied aircraft. The leading Allied ace was Billy Bishop of Canada, who downed 72. The leading American ace was Captain Eddie Rickenbacker, with 26 victories.